TCR-1-MEDIATED AND IL-1-MEDIATED CO-STIMULATION REVEALS AN IL-4-INDEPENDENT WAY OF T(H)2 CELL-PROLIFERATION

Previously, it has been shown that T(h)1 cells, when triggered solely via their TCR, are blocked from proliferation in response to IL-2, Her ein, we describe a similar characteristic for T(h)2 cells in that immo bilized mAb directed to the TCR blocked proliferation of T(h)2 cells i n response to IL-4, This 'proliferative block' was observed in all fou r T(h)2 cell clones tested, but not in a subline of one of the clones which has been cultured in vitro for several years, Addition of IL-1 n eutralized the proliferative block in all four T(h)2 cell clones. Surp risingly, blocking experiments with sIL-4R and anti-IL-4 mAb revealed that in three out of four T(h)2 cell clones this effect of IL-1 was IL -4-independent and could also not be blocked by cyclosporin A (CsA), I n contrast, the proliferation of one T(h)2 cell clone in response to t he TCR- and IL-1-mediated signals was indeed inhibited by sIL-4R, anti -IL-4 mAb and CsA, Thus, our data illustrate that in addition to the w ell-known IL-4-dependent proliferation, there also exists an IL-4-inde pendent, IL-1-mediated way of T(h)2 cell proliferation.